Fix textual printing of byte slices

[dsnet]

There are two bugs being fixed:

1. The hueristic for whether a slice of byte looks like text
   should check whether a rune IsPrint OR IsSpace, and not both.
   Only a single rune (i.e., U+0020) ever satisfies both conditions.

   Previously, it would print as:

   MyBytes{0x68, 0x65, 0x6c, 0x6c, 0x6f}
   

   and now it would now print as:

   MyBytes(MyBytes("hello"))
   

2. If we're printing as string, then we should set skipType=true
   since we already explicitly format the value with the type.

   Previously, it would print as:

   MyBytes(MyBytes("hello"))
   

   and now it would now print as:

   MyBytes("hello")
   

[dsnet]

\cc @neild.